The present invention relates to a fuel vapor processing apparatus for guiding fuel vapor generated in a fuel tank to a carbon canister and more particularly to a fuel vapor processing apparatus having a function to prevent a fuel tank from being over-filled during refueling.
As disclosed in Japanese Patent Application Laid-open No. Toku-Kai 2000-203282, the fuel vapor processing apparatus comprises an evaporative line (evaporative passage) for releasing the inner pressure of a fuel tank increased by the fuel vapor (evaporative gas) generated during traveling of a vehicle, a vent line (vent passage) for releasing the inner pressure increased by the fuel vapor generated during refueling and a vent switching valve for selectively opening onto the carbon canister (hereinafter referred to as just canister). The vent switching valve connects the evaporative passage with the canister when a fuel filler cap is closed and connects the vent passage with the canister.
In thus constituted fuel vapor processing apparatus, the evaporative passage communicates with the fuel tank through a fuel cut valve (FCV) provided above a fill up level. Further, in case where a vehicle body is slanted or in other cases, the fuel cut valve is closed to prevent fuel from flowing out from the fuel tank to the canister.
On the other hand, the vent passage communicates with the fuel tank through a liquid level restricting valve (fill up valve). When the liquid level of fuel reaches the fill up level at refueling, the liquid level restricting valve is closed. As a result, the inner pressure of the fuel tank rises, increasing the liquid level in the fuel filler pipe and preventing the fuel tank from being overfilled.
This type of the fuel vapor processing apparatus is strictly required to prevent evaporative gas from leaking out side. In order to realize the prevention of the leakage of evaporative gas with high reliability, it is desirable that the length of pipes having possibilities of leakage is shortened as far as possible, the number of connections is reduced, and the passage connecting the fuel tank and the canister is simplified.
However, the fuel cut valve for preventing fuel from flowing out during traveling and the liquid level restricting valve for preventing overfilling during refueling have an independent function, respectively and further these two valves communicate to two different lines of passages (evaporative passage and vent passage), respectively. Hence, it has been difficult to simplify the construction of the fuel vapor processing apparatus of this kind.
It is an object of the present invention to provide a fuel vapor processing apparatus capable of fulfilling two functions, that is, processing a fuel vapor generated at refueling and processing a fuel vapor generated during traveling of a vehicle, with a single evaporative passage line.
In order to attain the object, a fuel vapor processing apparatus comprises a canister for collecting the fuel vapor generated in a fuel tank, an evaporative passage for communicating between the canister and the fuel cut valve and for guiding the fuel vapor to the canister, a fuel cut valve interposed on the evaporative passage at a higher position than a fill up level in the fuel tank for introducing the fuel vapor, an orifice interposed between the evaporative passage and the fuel cut valve, a volume chamber interposed on the evaporative passage downstream of the orifice in the fuel tank for separating a liquid fuel from the fuel vapor, and a liquid level restricting valve communicating with the evaporative passage through a communicating hole provided at the bottom of the volume chamber and disposed below the volume chamber for closing the communicating hole at filling up so as to prevent overfilling.
The fuel vapor processing apparatus according to the present invention further includes a pressure control valve provided in the volume chamber for closing the evaporative passage so as to prevent the liquid fuel from entering the evaporative passage on the canister side.